Add Cache.getCachedBytes

This will replace the need to use CacheUtil.getCached, and is part of refactoring
CacheUtil to only do writing (it will be renamed to CacheWriter in a subsequent
change).

PiperOrigin-RevId: 312366040

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/Cache.java

@@ -279,6 +279,18 @@ public interface Cache {
    */
   long getCachedLength(String key, long position, long length);
 
+  /**
+   * Returns the total number of cached bytes between {@code position} (inclusive) and {@code
+   * (position + length)} (exclusive) of a resource.
+   *
+   * @param key The cache key of the resource.
+   * @param position The starting position of the data in the resource.
+   * @param length The length of the data to check. {@link C#LENGTH_UNSET} is permitted, and is
+   *     equivalent to passing {@link Long#MAX_VALUE}.
+   * @return The total number of cached bytes.
+   */
+  long getCachedBytes(String key, long position, long length);
+
   /**
    * Applies {@code mutations} to the {@link ContentMetadata} for the given resource. A new {@link
    * CachedContent} is added if there isn't one already for the resource.

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java

@@ -501,6 +501,29 @@ public final class SimpleCache implements Cache {
     return cachedContent != null ? cachedContent.getCachedBytesLength(position, length) : -length;
   }
 
+  @Override
+  public synchronized long getCachedBytes(String key, long position, long length) {
+    long endPosition = length == C.LENGTH_UNSET ? Long.MAX_VALUE : position + length;
+    if (endPosition < 0) {
+      // The calculation rolled over (length is probably Long.MAX_VALUE).
+      endPosition = Long.MAX_VALUE;
+    }
+    long currentPosition = position;
+    long cachedBytes = 0;
+    while (currentPosition < endPosition) {
+      long maxRemainingLength = endPosition - currentPosition;
+      long blockLength = getCachedLength(key, currentPosition, maxRemainingLength);
+      if (blockLength > 0) {
+        cachedBytes += blockLength;
+      } else {
+        // There's a hole of length -blockLength.
+        blockLength = -blockLength;
+      }
+      currentPosition += blockLength;
+    }
+    return cachedBytes;
+  }
+
   @Override
   public synchronized void applyContentMetadataMutations(
       String key, ContentMetadataMutations mutations) throws CacheException {

library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheTest.java

@@ -409,6 +409,72 @@ public class SimpleCacheTest {
         .isEqualTo(15);
   }
 
+  @Test
+  public void getCachedBytes_noCachedContent_returnsZero() {
+    SimpleCache simpleCache = getSimpleCache();
+
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ 100))
+        .isEqualTo(0);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(0);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ LENGTH_UNSET))
+        .isEqualTo(0);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ 100))
+        .isEqualTo(0);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(0);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ LENGTH_UNSET))
+        .isEqualTo(0);
+  }
+
+  @Test
+  public void getCachedBytes_withMultipleAdjacentSpans_returnsCachedBytes() throws Exception {
+    SimpleCache simpleCache = getSimpleCache();
+    CacheSpan cacheSpan = simpleCache.startReadWrite(KEY_1, /* position= */ 0);
+    addCache(simpleCache, KEY_1, /* position= */ 0, /* length= */ 25);
+    addCache(simpleCache, KEY_1, /* position= */ 25, /* length= */ 25);
+    simpleCache.releaseHoleSpan(cacheSpan);
+
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ 100))
+        .isEqualTo(50);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(50);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ LENGTH_UNSET))
+        .isEqualTo(50);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ 100))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ LENGTH_UNSET))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ 15))
+        .isEqualTo(15);
+  }
+
+  @Test
+  public void getCachedBytes_withMultipleNonAdjacentSpans_returnsCachedBytes() throws Exception {
+    SimpleCache simpleCache = getSimpleCache();
+    CacheSpan cacheSpan = simpleCache.startReadWrite(KEY_1, /* position= */ 0);
+    addCache(simpleCache, KEY_1, /* position= */ 0, /* length= */ 10);
+    addCache(simpleCache, KEY_1, /* position= */ 15, /* length= */ 35);
+    simpleCache.releaseHoleSpan(cacheSpan);
+
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ 100))
+        .isEqualTo(45);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(45);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 0, /* length= */ LENGTH_UNSET))
+        .isEqualTo(45);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ 100))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ Long.MAX_VALUE))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ LENGTH_UNSET))
+        .isEqualTo(30);
+    assertThat(simpleCache.getCachedBytes(KEY_1, /* position= */ 20, /* length= */ 10))
+        .isEqualTo(10);
+  }
+
   /* Tests https://github.com/google/ExoPlayer/issues/3260 case. */
   @Test
   public void exceptionDuringEvictionByLeastRecentlyUsedCacheEvictorNotHang() throws Exception {